Method for forming fin field effect transistor (FinFET) device structure with interconnect structure

ABSTRACT

A method includes a first metal layer formed over a substrate and a dielectric layer formed over the first metal layer. The method includes an adhesion layer formed in the dielectric layer and over the first metal layer, and the adhesion layer is a discontinuous layer. The method includes a second metal layer formed in the dielectric layer, and the adhesion layer is formed between the second metal layer and the dielectric layer. The second metal layer includes a via portion and a trench portion over the via portion, and the trench portion is wider than the via portion.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No. 14/799,258, filed on Jul. 14, 2015 and issuing as U.S. Pat. No. 9,536,826 entitled “Fin Field Effect Transistor (FINFET) Device Structure with Interconnect Structure”, and claims priority to U.S. Provisional Application No. 62/175,849, filed on Jun. 15, 2015, and entitled “Fin field effect transistor (FinFET) device structure with interconnect structure”, the entirety of each of which is incorporated by reference herein.

This application is related to the following commonly assigned application Ser. No. 14/813,775 “Fin field effect transistor (FinFET) device structure with interconnect structure”, the entirety of which is incorporated by reference herein.

BACKGROUND

Semiconductor devices are used in a variety of electronic applications, such as personal computers, cell phones, digital cameras, and other electronic equipment. Semiconductor devices are typically fabricated by sequentially depositing insulating or dielectric layers, conductive layers, and semiconductive layers of material over a semiconductor substrate, and patterning the various material layers using lithography to form circuit components and elements thereon. Many integrated circuits are typically manufactured on a single semiconductor wafer, and individual dies on the wafer are singulated by sawing between the integrated circuits along a scribe line. The individual dies are typically packaged separately, in multi-chip modules, for example, or in other types of packaging.

In the fabrication of semiconductor devices, the size of semiconductor devices has been continuously reduced in order to increase device density. Accordingly, a multi-layered interconnect structure is provided. The interconnect structure may include one or more conductive lines and via layers.

Although existing interconnect structures and methods of fabricating interconnect structures have been generally adequate for their intended purposes, they have not been entirely satisfactory in all respects.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It should be noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIG. 1 shows a three-dimensional view of an interconnect structure on a fin field effect transistor (FinFET) device structure, in accordance with some embodiments of the disclosure.

FIGS. 2A-2P show cross-sectional representations of various stages of forming a semiconductor device structure with an interconnect structure, in accordance with some embodiments of the disclosure.

FIG. 2P′ shows an enlarged representation of region A of FIG. 2P, in accordance with some embodiments of the disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, or examples, for implementing different features of the subject matter provided. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

Some variations of the embodiments are described. Throughout the various views and illustrative embodiments, like reference numbers are used to designate like elements. It should be understood that additional operations can be provided before, during, and after the method, and some of the operations described can be replaced or eliminated for other embodiments of the method.

Embodiments for forming a semiconductor structure with an interconnect structure are provided. The interconnect structure includes a number of metallization layers formed in a dielectric layer (such as inter-metal dielectric, IMD). One process for forming interconnect structures is the dual damascene process.

FIG. 1 shows a three-dimensional view of an interconnect structure on a fin field effect transistor (FinFET) device structure 100, in accordance with some embodiments of the disclosure.

The FinFET device structure 100 includes a substrate 102. The substrate 102 may be made of silicon or other semiconductor materials. Alternatively or additionally, the substrate 102 may include other elementary semiconductor materials such as germanium. In some embodiments, the substrate 102 is made of a compound semiconductor such as silicon carbide, gallium arsenic, indium arsenide, or indium phosphide. In some embodiments, the substrate 102 is made of an alloy semiconductor such as silicon germanium, silicon germanium carbide, gallium arsenic phosphide, or gallium indium phosphide. In some embodiments, the substrate 102 includes an epitaxial layer. For example, the substrate 102 has an epitaxial layer overlying a bulk semiconductor.

The FinFET device structure 100 also includes one or more fin structures 20 (e.g., Si fins) that extend from the substrate 102. The fin structure 20 may optionally include germanium (Ge). The fin structure 20 may be formed by using suitable processes such as photolithography and etching processes. In some embodiments, the fin structure 20 is etched from the substrate 102 using dry etch or plasma processes.

An isolation structure 22, such as a shallow trench isolation (STI) structure, is formed to surround the fin structure 20. In some embodiments, a lower portion of the fin structure 20 is surrounded by the isolation structure 22, and an upper portion of the fin structure 20 protrudes from the isolation structure 22, as shown in FIG. 1. In other words, a portion of the fin structure 20 is embedded in the isolation structure 22. The isolation structure 22 prevents electrical interference or crosstalk.

The FinFET device structure 110 further includes a gate stack structure including a gate dielectric layer 32 and a gate electrode 34. The gate stack structure is formed over a central portion of the fin structure 20. In some other embodiments, the gate stack structure is a dummy gate stack and is replaced later by a metal gate (MG) after high thermal budget processes are performed.

As shown in FIG. 1, spacers 36 are formed on the opposite sidewalls of the gate electrode 34. The source/drain (S/D) structures 24 are formed adjacent to the gate stack structure. The contact structures 40 are formed over the source/drain (S/D) structures 24, and a first metal layer 104 is formed over the contact structure 40. A trench-via structure 50 is formed over the first metal layer 104. A second metal layer (not shown) will be formed on the trench-via structure 50. The trench-via structure 50 is disposed between the first metal layer 104 and the second metal layer and is configured to electrically connect to the first metal layer 104 and the second metal layer.

FIG. 1 is a simplified view of the interconnect structure including a first metal layer and trench-via structure 50 over the fin field effect transistor (FinFET) device structure 100. Some features, such as the inter-layer dielectric (ILD) layer and doped regions, are not shown in FIG. 1.

FIGS. 2A-2P show cross-sectional representations of various stages of forming a semiconductor device structure with an interconnect structure 50 a, in accordance with some embodiments of the disclosure. FIGS. 2A-2P show a trench-first process for forming a dual damascene structure.

As shown in FIG. 2A, the semiconductor device structure 100 includes a substrate 102. The substrate 102 includes a first region 11 and a second region 12. IN some embodiments, the first region 11 is a dense region, and the second region 12 is an isolation region. The substrate 102 may be made of silicon or other semiconductor materials. Some device elements (not shown) are formed in the substrate 102. Device elements include transistors (e.g., metal oxide semiconductor field effect transistors (MOSFET), complementary metal oxide semiconductor (CMOS) transistors, bipolar junction transistors (BJT), high-voltage transistors, high-frequency transistors, p-channel and/or n channel field effect transistors (PFETs/NFETs), etc.), diodes, and/or other applicable elements. Various processes are performed to form device elements, such as deposition, etching, implantation, photolithography, annealing, and/or other applicable processes. In some embodiments, device elements are formed in the substrate 102 in a front-end-of-line (FEOL) process.

The substrate 102 may include various doped regions such as p-type wells or n-type wells). Doped regions may be doped with p-type dopants, such as boron or BF₂, and/or n-type dopants, such as phosphorus (P) or arsenic (As). The doped regions may be formed directly on the substrate 102, in a P-well structure, in an N-well structure, or in a dual-well structure.

The substrate 102 may further include isolation features (not shown), such as shallow trench isolation (STI) features or local oxidation of silicon (LOCOS) features. Isolation features may define and isolate various device elements.

As shown in FIG. 2A, a first dielectric layer 106 (such as inter-metal dielectric, IMD) is formed on the substrate 102, and a first metal layer 104 a and a second metal layer 104 b are embedded in first dielectric layer 106. The first metal layer 104 a is in the first region 11 and the second metal layer 104 b is in the second region 12. The first dielectric layer 106, first metal layer 104 a, and second metal layer 104 b are formed in a back-end-of-line (BEOL) process.

The first dielectric layer 106 may be a single layer or multiple layers. The first dielectric layer 106 is made of silicon oxide (SiOx), silicon nitride (SixNy), silicon oxynitride (SiON), dielectric material(s) with low dielectric constant (low-k), or combinations thereof. In some embodiments, the first dielectric layer 106 is made of an extreme low-k (ELK) dielectric material with a dielectric constant (k) less than about 2.5. In some embodiments, ELK dielectric materials include carbon doped silicon oxide, amorphous fluorinated carbon, parylene, bis-benzocyclobutenes (BCB), polytetrafluoroethylene (PTFE) (Teflon), or silicon oxycarbide polymers (SiOC). In some embodiments, ELK dielectric materials include a porous version of an existing dielectric material, such as hydrogen silsesquioxane (HSQ), porous methyl silsesquioxane (MSQ), porous polyarylether (PAE), porous SiLK, or porous silicon oxide (SiO₂). In some embodiments, the dielectric layer 106 is deposited by a plasma enhanced chemical vapor deposition (PECVD) process or by a spin coating process.

In some embodiments, the first metal layer 104 a and the second metal layer 104 b are independently made of copper (Cu), copper alloy, aluminum (Al), aluminum alloy, tungsten (W), tungsten alloy, titanium (Ti), titanium alloy, tantalum (Ta) or tantalum alloy. In some embodiments, the first metal layer 104 is formed by a plating method.

An etch stop layer 110 is formed over the first dielectric layer 106. The etch stop layer 110 may be a single layer or multiple layers. The etch stop layer 110 protects the underlying layers, such as the first dielectric layer 106, and also provides improved adhesion for layers formed subsequently.

The etch stop layer 110 is made of a metal-containing material, such as aluminum-containing material. In some embodiments, the aluminum-containing material is aluminum nitride, aluminum oxide or aluminum oxynitride. The aluminum-containing material may increase the speed of the semiconductor device 100.

A second dielectric layer 112 is formed over the etch stop layer 110. The second dielectric layer 112 may be a single layer or multiple layers. The second dielectric layer 112 is made of silicon oxide (SiOx), silicon nitride (SixNy), silicon oxynitride (SiON), dielectric material(s) with low dielectric constant (low-k), or combinations thereof. In some embodiments, the second dielectric layer 112 is made of an extreme low-k (ELK) dielectric material with a dielectric constant (k) less than about 2.5.

An antireflection layer 114 and a hard mask layer 116 are sequentially formed over the second dielectric layer 112. In some embodiments, the antireflection layer 114 is made of nitrogen-free material, such as silicon oxycarbide (SiOC). In some embodiments, the hard mask layer 116 is made of a metal material, such as titanium nitride (TiN), tantalum nitride (TaN), or tungsten nitride (WN). The hard mask layer 116 made of metal material is configured to provide a high etch selectivity relative to the second dielectric layer 112 during the plasma process.

A tri-layer photoresist structure 120 is formed on the hard mask layer 116. The tri-layer photoresist structure 120 includes a bottom layer 124, a middle layer 126 and a top layer 128. In some embodiments, the bottom layer 124 is a bottom anti-reflective coating (BARC) layer which is used to reduce reflection during the photolithography process. In some embodiments, the bottom layer 124 is made of nitrogen-free material, such as silicon rich oxide, or silicon oxycarbide (SiOC). In some embodiments, the middle layer 126 is made of silicon-based material, such as silicon nitride, silicon oxynitride or silicon oxide.

The top layer 128 may be a positive photoresist layer or a negative photoresist layer. In some embodiments, the top layer 128 is made of Poly (methyl methacrylate) (PMMA), Poly (methyl glutarimide) (PMGI), Phenol formaldehyde resin (DNQ/Novolac) or SU-8. In some embodiments, the ratio of the thickness of the bottom layer 124 to the thickness of the middle layer 126 is in a range from about 4 to about 8.

Afterwards, the top layer 128 is patterned to form a patterned top layer 128 as shown in FIG. 2B, in accordance with some embodiments of the disclosure. The patterned top layer 128 includes a first portion 128 a, a second portion 128 b and a third portion 128 c.

After the top layer 128 is patterned, the middle layer 126 is patterned by using the patterned top layer 128 as a mask as shown in FIG. 2C, in accordance with some embodiments of the disclosure. As a result, the pattern of the top layer 128 is transferred to the middle layer 126 to form the patterned middle layer 126.

After the middle layer 126 is patterned, the bottom layer 124 is patterned by using the patterned middle layer 126 as a mask as shown in FIG. 2D, in accordance with some embodiments of the disclosure.

Afterwards, the hard mask layer 116 is patterned by using the patterned bottom layer 124 as a mask as shown in FIG. 2E, in accordance with some embodiments of the disclosure. Afterwards, the tri-layer photoresist structure 120 is removed by an etching process. Therefore, the patterned hard mask layer 116 is obtained, and it includes a first portion 116 a, a second portion 116 b and a third portion 116 c. The first width W₁ is formed between the first portion 116 a and the second portion 116 b. The second width W₂ is formed between the second portion 116 b and the third portion 116 c. In some embodiments, the first width W₁ is substantially equal to the second width W₂.

After the hard mask layer 116 is patterned, a second photoresist structure 220 is formed over the patterned hard mask layer 116 as shown in FIG. 2F, in accordance with some embodiments of the disclosure. The second photoresist structure 220 includes a bottom layer 224, a middle layer 226 and a top layer 228.

The top layer 228 of the second photoresist structure 220 is firstly patterned to form a patterned top layer 228 as shown in FIG. 2G, in accordance with some embodiments of the disclosure. The patterned top layer 228 includes a first portion 228 a, a second portion 228 b and a third portion 228 c. A third width W₃ is formed between the first portion 228 a and the second portion 228 b. A fourth width W₄ is formed between the second portion 228 b and the third portion 228 c. The third width W₃ is substantially equal to the fourth width W₄. The third width W₃ between the first portion 228 a and the second portion 228 b is smaller than the first width W₁ (as shown in FIG. 2E) between the first portion 116 a and the second portion 116 b of the patterned hard mask layer 116.

Afterwards, the middle layer 226 is pattered by using the patterned top layer 228 as a mask as shown in FIG. 2H, in accordance with some embodiments of the disclosure.

After the middle layer 226 is pattered, the bottom layer 224 and a portion of the antireflection layer 114 is removed as shown in FIG. 2I, in accordance with some embodiments of the disclosure. The portion of antireflection layer 114 is removed by a first etching process 310 to form a first recess 302 a in the first region 11 and a second recess 302 b in the second region 12. The sidewalls of the recess 302 are vertical to the antireflection layer 114. The width of the first recess 302 a is substantially equal to the width of the second recess 302 b.

The first plasma process 310 includes using a first etch gas including oxygen gas (O₂), carbon dioxide (CO₂) or another applicable gas. In addition to gas, the first etching process 310 may be fine-tuned with various parameters, such as pressure, power, temperature and/or other suitable parameters.

After forming the first recess 302 a and the second recess 302 b, the antireflection layer 114 is etched through and a portion of the second dielectric layer 112 is removed by a second etching process 330 as shown in FIG. 2J, in accordance with some embodiments of the disclosure.

As a result, the recess 302 is elongated to form a first opening 304 a and a second opening 304 b. It should be noted that the sidewalls of the first opening 304 a and second opening 304 b are vertical to the second dielectric layer 112. In other words, the first opening 304 a and the second opening 304 b both have a substantially vertical profile.

The second etching process 330 is performed by using a second etch gas including fluorine-containing gas, nitrogen (N₂), oxygen (O₂) or combinations thereof. The fluorine-containing gas includes nitrogen hexafluoroethane (C₂F₆), tetrafluoromethane (CF₄), trifluoromethane (CHF₃), difluoromethane (CH₂F₂), octofluoropropane (C₃F₈), octofluorocyclobutane (C₄F₈), or combinations thereof.

Afterwards, the second photoresist structure 220 is removed as shown in FIG. 2K, in accordance with some embodiments of the disclosure. Therefore, the patterned hard mask layer 116 is exposed.

After the second photoresist structure 220 is removed, the second dielectric layer 112 and the etch stop layer 110 are etched through to expose the first metal layer 104 by a third etching process 350 as shown in FIG. 2L, in accordance with some embodiments of the disclosure.

Therefore, a first via opening 306 a and a first trench opening 308 a are formed and they collectively constitute a first trench-via structure for use as a dual damascene cavity. The first via opening 306 a has a first width D₁. In some embodiments, the first width D₁ is in a range from about 30 nm to about 60 nm. The first trench opening 308 a has a third width D₃. In some embodiments, the third width D₃ is greater than the first width D₁.

If the first width D₁ is smaller than 30 nm, the dimensions are too small to fill the conductive material. If the first width D₁ is greater than 60 nm, the pitch between two adjacent via openings may be smaller than the predetermined value.

The third etching process 350 is performed by using a third etch gas including fluorine-containing gas, nitrogen (N₂), oxygen (O₂) or combinations thereof. The fluorine-containing gas includes nitrogen hexafluoroethane (C₂F₆), tetrafluoromethane (CF₄), trifluoromethane (CHF₃), difluoromethane (CH₂F₂), octofluoropropane (C₃F₈), octofluorocyclobutane (C₄F₈), or combinations thereof.

The third etch gas used in the third etching process 350 further includes a diluting gas, such as an inert gas like argon (Ar) or helium (He). The diluting gas is used to decrease the loading effect.

After the third etching process 350, an adhesion layer 130 is formed on sidewalls and the bottom surfaces of the via openings 306 a, 306 b and trench openings 308 a, 308 b as shown in FIG. 2M, in accordance with some embodiments of the disclosure. In addition, the adhesion layer 130 is also formed on the hard mask layer 116.

The adhesion layer 130 is used to provide improved adhesion for layers formed subsequently. In some embodiments, the adhesion layer 130 is made of titanium (Ti), titanium nitride (TiN), tantalum (Ta), tantalum nitride (TaN), or aluminum nitride (AlN).

After formation of the adhesion layer 130, a portion of the etch stop layer 110 is removed to expose the first metal layer 104 a and the second metal layer 104 b by a fourth etching process 370, as shown in FIG. 2N, in accordance with some embodiments of the disclosure.

In some embodiments, the fourth etching process 370 is a dry etching process, such as plasma process. During the fourth etching process 370, the electric field concentrates at corners region of the opening. Therefore, corner region may be damaged. As shown in FIG. 2N, a portion of the adhesion layer 130 is also removed, especially at corner regions. As a result, the adhesion layer 130 becomes a discontinuous layer.

The adhesion layer 130 includes a first portion 130 a and a second portion 130 b below the first portion 130 a. The first portion 130 a is adjacent to or lines with the trench openings 308 a, 308 b, and the second portion 130 b is adjacent to or lines with the via openings 306 a, 306 b.

In some embodiments, the first portion 130 a of the adhesion layer 130 has an extended bottom surface in a horizontal direction (in parallel to the top surface of the metal layer 104). The extended bottom surface is larger than a top surface of the first portion 130 a of the adhesion layer 130.

In some embodiments, the second portion 130 b of the adhesion layer 130 has a sloped surface. In some embodiments, the second portion 130 b of the adhesion layer 130 has a top surface which is not parallel to a top surface of the first metal layer 104 a, 104 b.

If there is no adhesion layer on the first via opening 306 a and the second via opening 306 b, during the fourth etching process 370 (as shown in FIG. 2N), the first metal layers 104 a and the second metal layer 104 b are exposed and some by-products (such as metal-containing material) may form on the first via opening 306 a and the second via opening 306 b. When undesirable by-products are deposited on the sidewalls of the first via opening 306 a and the second via opening 306 b, the widths of the via openings 306 a, 306 b may become smaller, and the conductive feature 142 are difficult to fill into the via openings 306 a, 306 b. In addition, some metal-containing material may re-sputter on the sidewalls of the via openings 306 a, 306 b. As a result, the adhesion between the conductive feature 142 and the second dielectric layer is decreased. Therefore, the adhesion layer 130 is formed before the first metal layers 104 a and the second metal layer 104 b are exposed.

After the fourth etching process 370, a conductive feature 142 is formed in the trench openings 308 a, 308 b, the via opening 306 a, 306 b and on the hard mask layer 116, as shown in FIG. 2O, in accordance with some embodiments of the disclosure.

The conductive feature 142 is electrically connected to the first metal layer 104. In some embodiments, the conductive feature 142 is referred to a second metal layer. The first metal layer 104 embedded in the first dielectric layer 106 and the conductive feature 142 embedded in second dielectric layer 112 construct a portion of the interconnect structure 50 a. In some embodiments, the conductive feature 142 is made of copper (Cu), copper alloy, aluminum (Al), aluminum alloys, or combinations thereof.

It should be noted that the adhesion between the dielectric layer 112 (especially low-k material) and the conductive feature 142 is poor. If no adhesion layer 130 formed between the dielectric layer 112 and the conductive feature 142, the conductive feature 142 may be shrunk by a baking process which is performed after FIG. 2P. Therefore, the adhesion layer 130 is configured to increase the adhesion and prevent the shrinkage problem of the conductive feature 142.

Afterwards, the antireflection layer 114, the hard mask layer 116 and some conductive feature 142 out of the trench openings 308 a, 308 b are removed, as shown in FIG. 2P, in accordance with some embodiments of the disclosure. FIG. 2P′ shows an enlarged representation of region A of FIG. 2P, in accordance with some embodiments of the disclosure. In some embodiments, the antireflection layer 114 and hard mask layer 116 are removed by a chemical mechanical polishing (CMP) process.

As shown in FIG. 2P, a portion of the conductive feature 142 is surrounded by the adhesion layer 130, but not all of the conductive feature 142 is surrounded by the adhesion layer 130. The conductive feature 142 includes an upper portion (also called a trench portion) 142 a, a lower portion 142 c (also called a via portion), and a middle portion (also called an interface portion) 142 b between the upper portion 142 a and the lower portion 142 c. No obvious interfaces exist between the upper portion 142 a and the middle portion 142 b, and between the middle portion 142 b (or interface portion) and the lower portion 142 c. The dashed lines shown in FIG. 2P are used to clarify the disclosure.

The upper portion 142 a has a constant width W₅, and the lower portion 142 c has a constant width W₆. However, the middle portion 142 b has a tapered width which is gradually tapered from the upper portion 142 a to the lower portion 142 c. In other words, the middle portion 142 b has a pair of curved sidewalls. The width W₅ is larger than the width W₆, and the tapered width is smaller than the width W₅ and larger than the width W₆.

It should be noted that the adhesion layer 130 is formed between the conductive feature 142 and the second dielectric layer 112, and portions of the upper portion 142 a and the lower portion 142 c of the conductive feature 142 are not formed on the adhesion layer 130. But, a portion of the middle portion 142 b of the conductive feature 142 is not formed on the adhesion layer 130. Instead of being in contact with the adhesion layer 130, the middle portion 142 b of the conductive feature 142 is in direct contact with the second dielectric layer 112 because the adhesion layer 130 is a discontinuous layer.

As mentioned above, the adhesion layer 130 includes the first portion 130 a and the second portion 130 b. As shown in FIGS. 2P and 2P′, the first portion 130 a lines with the upper portion 142 a of the conductive feature 142, and the second portion 130 b lines with the lower portion 142 c of the conductive feature 142. A portion of the interconnect structure is surrounded by the etch stop layer. More specifically, a portion of the conductive feature 142 is surrounded by the etch stop layer 110.

As mentioned above, during the fourth etching process 370 (as shown in FIG. 2N), if no adhesion layer 130 is formed on the first via opening 306 a and the second via opening 306 b, the first metal layers 104 a, 104 b are exposed and some by-products (such as metal-containing material) may form on the first via opening 306 a and the second via opening 306 b. As a result, undesirable by-products are deposited on the sidewalls of the via openings 306 a, 306 b. The widths of the first via opening 306 a and the second opening 306 b become smaller, and the conductive feature 142 are difficult to fill into the first via opening 306 a and the second opening 306 b.

In addition, some metal-containing material may re-sputter on the sidewalls of the first via opening 306 a and the second via opening 306 b. As a result, the adhesion between the conductive feature 142 and the second dielectric layer is decreased. The conductive feature 142 may easily become delaminated while performing a baking process after the removing process shown in FIG. 2P. In order to prevent the delamination problem and increase the adhesion between the conductive feature 142 and the second dielectric layer 112, the adhesion layer 130 is formed as shown in FIG. 2M before the metal layers 104 a, 104 b are exposed. The adhesion layer 130 protects the sidewalls of the first via opening 306 a and the second via opening 306 b from being polluted. Furthermore, the adhesion layer 130 increases the adhesion between the conductive feature 142 and the second dielectric layer 112.

Embodiments for forming a semiconductor device structure and method for formation of the same are provided. The semiconductor device structure includes a FinFET structure formed over a substrate, and an interconnect structure formed over the FinFET structure. The interconnect structure includes a dual damascene structure with a trench-via structure. A trench opening and a via opening are formed in a dielectric layer, and a conductive feature is filled into the trench opening and the via opening to form the trench-via structure.

An adhesion layer is formed on the trench-via structure before the first metal layer is exposed. The adhesion layer is a discontinuous layer and has an extending portion. The adhesion layer is configured to improve the adhesion between the dielectric layer and conductive feature. Therefore, the delamination problem of the conductive feature is prevented. Furthermore, the performance of the semiconductor device structure is improved.

In some embodiments, a semiconductor device structure is provided. The semiconductor device structure includes a first metal layer formed over a substrate and an interconnect structure formed over the first metal layer. The interconnect structure includes an upper portion, a middle portion and a lower portion, the middle portion is connected between the upper portion and the lower portion. The upper portion and the lower portion each have a constant width, and the middle portion has a tapered width which is gradually tapered from the upper portion to the lower portion.

In some embodiments, a method for forming a semiconductor device structure is provided. The method includes a first metal layer formed over a substrate and a dielectric layer formed over the first metal layer. The method includes an adhesion layer formed in the dielectric layer and over the first metal layer, and the adhesion layer is a discontinuous layer. The method includes a second metal layer formed in the dielectric layer, and the adhesion layer is formed between the second metal layer and the dielectric layer. The second metal layer includes a via portion and a trench portion over the via portion, and the trench portion is wider than the via portion.

In some embodiments, a method for forming a semiconductor device structure is provided. The method includes forming a first metal layer over a substrate and forming an etch stop layer over the first metal layer. The method includes forming a dielectric layer over the etch stop layer and forming a trench opening and a via opening in the dielectric layer. The method includes a forming an adhesion layer on sidewalls and bottom surfaces of the trench opening and the via opening and removing a portion of the etch stop layer directly above the first metal layer and removing a portion of the adhesion layer to expose a portion of the dielectric layer. The method includes a filling a second metal layer in the via opening and the trench opening, and the second metal layer is electrically connected to the first metal layer.

The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. 

What is claimed is:
 1. A method for forming a semiconductor device structure, comprising: forming a first metal layer over a substrate and an etch stop layer over the first metal layer; forming a dielectric layer over the etch stop layer; forming a trench opening and a via opening in the dielectric layer; depositing an adhesion layer on sidewalls and bottom surfaces of the trench opening and the via opening; using a plasma etching process, removing a portion of the etch stop layer directly above the first metal layer and removing a portion of the adhesion layer to expose a portion of the dielectric layer, wherein during the plasma etching process, an electric field concentrates at corners region between the via opening and the trench opening; and filling a second metal layer in the via opening and the trench opening, wherein the second metal layer is electrically connected to the first metal layer.
 2. The method for forming the semiconductor device structure as claimed in claim 1, further comprising: forming a patterned hard mask layer over the dielectric layer; and patterning the dielectric layer by the patterned hard mask layer, such that the trench opening is over the via opening, and a width of the trench opening is larger than a width of the via opening.
 3. The method for forming the semiconductor device structure as claimed in claim 1, wherein after removing the portion of the adhesion layer to expose the portion of the dielectric layer, the adhesion layer becomes a discontinuous layer.
 4. The method for forming the semiconductor device structure as claimed in claim 3, wherein a discontinuity of the discontinuous layer is disposed at a middle portion interposing the trench opening and the via opening.
 5. The method for forming the semiconductor device structure as claimed in claim 1, wherein the depositing the adhesion layer includes forming a conformal layer on sidewalls of the trench opening and via opening.
 6. The method of claim 1, wherein the depositing the adhesion layer includes depositing at least one of titanium (Ti), titanium nitride (TiN), tantalum (Ta), tantalum nitride (TaN), or aluminum nitride (AlN).
 7. The method of claim 1, wherein the depositing the adhesion layer is performed on a top surface of the dielectric layer and wherein during the plasma etching process removing the portion of the adhesion layer, the adhesion layer is not removed from the top surface of the dielectric layer.
 8. The method of claim 7, further comprising: performing a chemical mechanical polish to remove the adhesion layer from the top surface of the dielectric layer.
 9. A method of fabricating a semiconductor device, the method comprising: forming a continuous opening in a dielectric layer disposed on the substrate, wherein the continuous opening includes a via opening and a trench opening; forming a conformal adhesion layer on sidewalls of the continuous opening and on a top surface of the dielectric layer; and after forming the conformal adhesion layer, etching a layer underlying the continuous opening, wherein during the etching, a portion of the adhesion layer is removed at an interface between the via opening and the trench opening and wherein the conformal adhesion layer remains on the top surface of the dielectric layer after the etching the layer.
 10. The method of claim 9, wherein the removed portion of the adhesion layer provides for a discontinuous layer.
 11. The method of claim 10, wherein after the etching, the discontinuous layer has an upper portion on a sidewall of the trench opening and a lower portion on a sidewall of the via opening.
 12. The method of claim 9, wherein the etching is a dry etching.
 13. The method of claim 12, wherein the etching is a plasma etching.
 14. The method of claim 13, wherein an electric field concentrates at the removed portion of the adhesion layer during the plasma etching.
 15. The method of claim 9, further comprising: after the etching the layer, depositing a conductive material in the via opening and the trench opening over the adhesion layer; and performing a chemical mechanical polishing (CMP) of the deposited conductive material, wherein the CMP removes the adhesion layer remaining on the top surface of the dielectric layer.
 16. A method, the method comprising: providing a semiconductor substrate having an etch stop layer disposed thereover; depositing a dielectric layer over the etch stop layer; forming a via opening and an overlying trench opening in the dielectric layer, wherein the via opening and the trench opening are vertically aligned and a corner region is formed at an interface between the via opening and the trench opening; forming a conformal adhesion layer on sidewalls of the via opening and the trench opening; and after forming the conformal adhesion layer, plasma etching the etch stop layer disposed at a bottom of the via opening underlying the continuous opening, wherein during the plasma etch an electric field concentrates at the corner region.
 17. The method of claim 16, wherein the plasma etch removes a portion of the conformal adhesion layer to form a discontinuous layer.
 18. The method of claim 16, wherein the plasma etch exposes the dielectric layer at the corner region.
 19. The method of claim 16, wherein the plasma etching exposes a metal layer underlying the etch stop layer.
 20. The method of claim 16, further comprising: after the plasma etching, filling the via opening and the overlying trench opening with conductive material. 